Sulfur regulation of boron doping and growth behavior for high-quality diamond in microwave plasma chemical vapor deposition

In this work, sulfur addition has been employed on the boron-doped diamond growth process, and a significant regulation of the boron doping and the growth behavior has been realized by microwave plasma chemical vapor deposition. It is interesting to find that the sulfur incorporation will lead to an accordant evolution on the boron doping efficiency, hole mobility and concentration, crystal quality, surface morphology, and growth rate. In the presence of sulfur with appropriate dosage, for a boron-to-carbon ratio of only 2.5 ppm in gas phase during growth, a very high doping concentration of 1.2 × 1019 at/cm3 has been achieved, indicative of a very efficient boron doping. Besides, the hole mobility of the sample is 853 cm2/V s at 300 K, which is better than the state of the art for p-type doping in diamond. The regulation mechanism of the sulfur addition will be discussed from the point of view of sulfur-induced plasma change and possible B–S complex formation. This study may provide an effective way for high-quality p-type conductive diamond layer growth and further for the potential diamond-based opto-electronic device applications.